Levels of Light on Earth and Biological Responses

Environmental Conditiona Spherical Photon Fluxa, 400-700 nm
(photons/m2/s)		 Biological Response Notes and References
Table 1, from Life Under the Sun, 2002, Yale University Press.
Clear Midday
~1021
 Saturation of photosynthesis in "sun-loving" plants
(continuous exposure)		 Light level is species dependentb
Cloudy Midday
~1020
 Saturation of photosynthesis in "shade-loving" plants
(continuous exposure)		 Light level is species dependentb
Clear Sunset
~1019
 Increase in Gonyaulax circadian period
(single 4 hr red light pulse)		 Threshold for bioluminescence rhythmc
Clear, Early Twilight
~1018
 Seed Germination (LFR)
(1 sec red light pulse)		 Threshold for Low Fluence-Responsed
Clear, Late Twilight
~1017
 Negative phototaxis in Dictyostelium amoebas
(continuous white light exposure)
Higher light levels-negative phototaxis (AX-2 strain)e
Lower light levels- positive phototaxis (AX-2 strain)e
Midnight
Clear, Full Moon
~1016
 Photophobic response in Stentor coeruleus
(continuous red light exposure)
Threshold for light avoidance in 'Stella' strainf
Midnight
Clear, New Moon
~1015
 Human color vision Threshold corresponding to ~10-2 milliLambertsg
Midnight
Cloudy, New Moon
~1014
 Seed germination (VLFR)
(1 sec red light pulse)		 Threshold for Very Low Fluence-Responsed
-

~1013
 -

-

-

~1012
 Positive phototaxis in Dictyostelium slugs
(continuous white light exposure)		 Threshold level for NC4 strainh
Threshold for AX2 strain is ~100-fold loweri
-

~1011
 -

-

-

~1010
 Human Vision
(1 millisecond green light exposure)		 Threshold corresponding to ~10-6.5 milliLambertse, j
-

~109
 Phototropism in Phycomyces
(continuous blue light exposure)		 Threshold levelk
-

~108
 -

-

-

~107
 Adaptation acceleration in Phycomyces
(35 min red light pulse)		 Threshold Levell

References
a. Based on measurements in Erlangen, Germany given in K.M. Hartmann, 1995, International Symposium on Weed and Crop Resistance to Herbicides. Cordoba, Spain. Simultaneous measurements of spherical illuminance, a measure of the light level sensed by the human eye, ranged from about 105 lux during a clear midday to about 10-3 lux during a cloudy midnight at new moon. Lux (lx) to Lumens (lm) to Candelas (cd): 1 lx = 1 lm/m2 = 1 cd⋅sr/m2
b. F.B. Salisbury and C.W. Ross, 1991, Plant Physiology, Belmont, CA, Wadsworth, Inc.
c. T. Roenneberg and J.W. Hastings, 1991, Photochem Photobiol 53, 525-33.
d. K. M. Hartmann and W. Nezadal, 1990, Naturwissenschaften 51, 158-63.
e. D. -P. Hader and B. Vollersten, 1991, Acta Protozool 30, 19-24.
f. C.B. Hong et al., 1987, Arch Microbiol 147, 117-20.
g. P. Buser and M. Imbert, 1995, Vision. Cambridge, MIT Press. Lamberts (L) to Candelas (cd): 1 L = (104/π) cd/m2
h. K.L. Poff and D.-P. Hader, 1984, Photochem Photobiol 39, 433-36.
i. D.-P. Hader and A. Haser, 1991, Bot Acta 104, 200-5.
j. S. Hecht et al., 1942, J Gen Physiol 25, 819-40. Lamberts (L) to Candelas (cd): 1 L = (104/π) cd/m2
k. K. Bergman et al., 1969, Bacteriol Rev 33, 99-150; P.A. Ensminger et al., 1990, Photochem Photobiol 51, 681-7.
l. P. Galland et al., 1989, Photochem Photobiol 49, 485-91; X.-Y. Chen et al., 1993, Photochem Photobiol 58, 425-31.

Peter A. Ensminger, ensmingr@twcny.rr.com
last updated: Feb 4, 2008